Tax treaty definitions set scope and mutual mechanisms for information exchange and assistance in collection of tax claims. Article 4 defines the treaty's territorial scope and identifies the competent authorities of each Contracting Party. It sets out key terms - person, company, publicly traded company, principal class of shares, recognised stock exchange, collective investment fund or scheme, public collective investment fund, tax, information, information gathering measures, and assistance in collection measures - and defines requesting Party and requested Party roles. Undefined terms take their meaning under the domestic law of the applying Contracting Party unless context or a competent-authority agreement provides otherwise.